For more on the WTA's Original 9, read our write-ups on each of tennis' trailblazing women.

At the 1970 US Open, Rosie Casals had a fortnight to remember. The 21-year-old reached her first major singles final, putting Margaret Court’s calendar Grand Slam at risk when forcing a deciding third set against the Australian. She also had a conversation that would impact not only her own career, but every woman pursuing one in professional tennis.

With fellow players Billie Jean King and Nancy Richey, the trio met with Gladys Heldman during the tournament to express their grievances over unequal pay and opportunity when comparing to their male peers. What came out of it was a decision that changed tennis history forever.

“We were going to go out to the Pacific Southwest with Jack Kramer, and we saw what the prize money was. He said, ‘I don’t care if the women come or not,’” Casals told Tennis Channel. “So, we didn’t come. We decided we were going to boycott.”


Original 9: Rosie Casals on the "big change in our way of thinking"

Original 9: Rosie Casals on the "big change in our way of thinking"

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Heldman, who had been unsuccessful in getting Kramer to reduce a pay inequality ratio greater than 8 to 1, would line up Philip Morris as a sponsor for a tournament she would stage herself, and just less than two weeks after her US Open runner-up effort, Casals became one of the Original 9 on September 23, 1970, at the Houston Racquet Club. In going out on their own, these nine pioneers would discover how to promote themselves as world-class athletes, no longer lumped as an afterthought with male players.

“I think we were happy that at least someone payed attention to us and believed in us. If it wasn’t for Virginia Slims, women’s tennis wouldn’t be where it is now,” said Casals. “So many things have happened with them. They showed us marketing, and they had the money to back everything up. We were no longer sharing anything with the men, so it was a big change in our way of thinking… they were very helpful in plotting out careers.”

Casals went down in the record books as the first woman to win a Virginia Slims Invitational after rallying from a set down to beat Australian Judy Dalton in the Houston final. The victory on court was memorable, and the check Casals received as the winner was gratifying. But for the San Francisco native, the courageous act she took alongside eight other women is what has stuck with her to this day.

“The Original 9 took the chance and made it happen for everybody else,” said Casals. “I’m happy and proud to have been a part of it, to start it and seen a vision along with Billie Jean, who was our leader. Because without that vision, without that leadership, it would’ve been very hard to get to where tennis is right now.”

As Casals, who turned 72 Wednesday, aptly puts it, “We’ve come a long way baby.”

Original 9: Rosie Casals on the "big change in our way of thinking"

Original 9: Rosie Casals on the "big change in our way of thinking"